This invention relates to an optical information recording card using a polymer blend as the recording material in which digital information can be thermally written by a semiconductor laser beam.
With the rapid advance of semiconductor lasers in recent years, much vigorous efforts have been devoted to the development of optical information recording discs and cards using a thermal mode recording material. In the thermal mode recording, information is input in the form of heat energy and is recorded and read by utilizing a change in a physical property or state of the recording material, such as a magnetic change, photochromic change or phase transition. For some purposes information storage systems of this category have already been put into practical use.
Well known thermal mode recording materials are some alloys or intermetallic compounds which are fundamentally composed of Al, Ten-key, Bi, Set, Tb, Co, Fe and/or In. Besides, there are proposals for use of organic pigments of cyanine type, use of a colloidal organic material in which silver particles are dispersed or use of a metal salt for precipitation of a metal by electroless plating. A typical method for recording information is forming tiny pits in the recording layer by utilizing thermal deformation of the recording material. Also it is known to write and read information by utilizing a thermally caused phase transition of the recording material from a noncrystalline state to a crystalline state and/or vice versa. Usually a semiconductor laser beam is employed as the heating means for recording information. The laser beam is focussed to a very small spot on the recording layer surface and is guided so as to digitally and one-dimensionally write information into the recording layer.
As to the aforementioned metallic recording materials, a disadvantage is that most of the essential metals have toxicity and, hence, have to be handled with great care. This becomes a particularly serious matter of concern in the cases of information recording cards with which human bodies very frequently make direct contact. Besides, the metallic recording materials are liable to oxidation or some corrosion and do not possess good storability. At present these shortcomings are coped with by providing a protective film on the recording layer of each recording medium. Nevertheless, the recording layer gradually deteriorates by oxidation or partial corrosion and consequently becomes low in recording sensitivity and/or reading sensitivity. From an economical point of view, high cost of equipment for vapor deposition or sputtering of the metallic recording materials is also an important consideration.
Nonmetallic optical information recording materials have not yet proved to be practicable and sufficiently stable.